There is no one-best-recipe.
Your vassals should never have too many titles - in this case they will have power to singlehandedly overthrow you and usurp your title or make you to lower crown authority or taxes or levy size. And be sure - there will be time when they want it.
Also don't give titles to someone who hates you - in this case make them your vassal's vassal - this is a suitable solution for unlanded sons or brothers. It also makes them harder to raise war for your crown, because they should firstly became duchies, and this involves war with their liege, whom they may hate no so strongly.
Give titles to ppl who have Content trait (+50 relations), to someone with same sins and virtues as you, also try to make your king as good as your can - virtuous, kind, just, prestigious, pious.
Look for vassals' background - don't give land title to priests and mayors - they will have "Wrong government type" penalty.
Respect - is everything. You can fight with rebel vasslas, but not with all of them at the same time.
Hope they will be helpful!
I would go with option one. You say that it leaves you less profit, but that is only partially true. Since you will eventually die and play as your heir, all of that money will drop right back into your pocket. It is possible that your heir will waste some of it, but not a large amount. Most of the money he earns will go back into his properties, and so that gold will end up benefiting you in the long run.
As an additional bonus, if/when your heir wins the war, he will get money and prestige from your non-heir vassal.
Best Answer
It is very important for numerous reasons that your vassals have a good opinion of you, especially those who hold landed titles. There is a large opinion-penalty for people of different cultures and an even larger one for people of a different religion. For that reason you should generally avoid to give any titles to people not of your religion and culture.
When you give an Orthodox character a Muslim county, the first thing they will do will usually be to set their court chaplain to "Proletylize" that county and make it Orthodox (especially when they have the "Zealous" trait). When you want your whole realm to be of one religion (you do!), then that's one more reason to avoid giving titles to infidels and heretics.
The only advantage it might have to have vassals who are of the same religion/culture as their counties is that automatically generated characters in that county will usually be of the local culture. That means these characters will like their boss better which means the vassal has a lower chance of getting assassinated or having to deal with rebellions. But this is usually a very minor aspect.
There might also be very rare situations in which a certain religious mechanic gives a vassal an unique advantage from which you also benefit. For example, their religion might give a vassal a Casus Belli against a neighbor which you don't have and give them the opportunity to conquer land for you which you couldn't conquer yourself (doesn't work with holy wars, by the way. A vassal can't declare holy wars when their liege is of a different religion than they are). But that's something extremely circumstantial.